Turbidity

[Pibuz]

Sorry guys, I was just testing again the turbidity parameter for I'm writing a small tutorial about lighting for the Indigo italian forum. I just experienced something I was not expecting, indeed.
I was sure that low turbidity parameters would actually lead to more blue images, and high values to more yellow-orange images.
So I did two tests and these are the results: the value of 2 gives more blueish tones than 1.5, which confuses me a little.

I have to say that the render with turbidity=2 was done with the 2.2.6 version, while the render with turbidity=1.5 was done with the 2.2.7 version.

So I ask you all: is that all correct? Is this some kind of bug? I was wrong assuming that 1.5 would have led to a more blue-tinted image?

Thank you for your anwers!

[Zom-B]

Turbidity was always quite some strange parameter... afaik 1.8 was the lowest giving correct results.
Anyway, I would love to have it working as supposed...

[Pibuz]

In SkIndigo we have a scrollbar, so I guess 1.5 is the real lowest possible parameter, and 7.5 is the highest.

[Pibuz]

Here are some other comparisons. I find that the turbidity parameter has been somehow heavily corrupted by other lines of the code. The maximum turbidity leads to a slightly coloured image, while in the past would have meant a really orange overall tone. I guess this is a bug.

[CTZn]

I do not think that turbidity should be set below 2 (is that parameter an exponent ?), or you may be stressing the model a bit.

[Pibuz]

Thank you CTZn for following me.

I'm now asking for help here: is anyone still using a previous version of Indigo? Better: SkIndigo?

I'd ask if it could be possible to do four tests with the turbidity values I've set for my latest test, and post the result, a detailed model is not needed: a cuve with a plane in the background will do the job. I think the overall atmosphere will come out quite different, using version 2.2.6 or previous.

[mr_jo]

... is anyone still using a previous version of Indigo? Better: SkIndigo?
I'd ask if it could be possible to do four tests with the turbidity values I've set for my latest test, and post the result,

Hi Pibuz and all, I'm using Indigo 2.2.1 and SkIndigo 2.2.3.
I've done four test with your turbidity values, White Point set to E
here's the result

[OnoSendai]

IIRC, turbidity should always be set in the range 2 to 6, due to limitations of the original model.

[Pibuz]

turbidity should always be set in the range 2 to 6, due to limitations of the original model.

That's something Whaat has to fix in SkIndigo then
OR you have to increase the range Ono BTW this is a silly thing, I know..

mr_jo:
Thank you very much for your tests. really informative.
Now, for a proper comparison I'd say we have to test again with "accepted" values.
can you do some tests with Turbidity equal to 2 - 4.5 - 6?
I'll do the same with 2.2.7 version. Thank you a lot!

[mr_jo]

Hi Pibuz, here's the result
P.S. I've changed a little bit the gray from the previous test